Rotation lasers used for marking points and for defining reference planes on construction sites or reference lines on objects such as e.g. walls, floors or ceilings have been used for many years in the industrial sector and in building and construction. They can be used to project horizontal planes, vertical planes, or else planes inclined in a defined manner, which offer assistance for orientation or positioning on objects.
Rotation lasers generally comprise a transmitting unit comprising a laser light source for generating a laser beam. The rotation laser furthermore has an optical system comprising one or a plurality of lenses, and a deflection means rotatable about a rotation axis and serving for the directional emission of the laser beam. If a rotating laser beam in the visible wavelength range is emitted and if said laser beam impinges on an object, then a reference line is visible there as a basis for further measures. In order that the reference plane or on a wall just the reference line actually has the desired inclination angle in space or is actually horizontal or vertical, firstly the rotation laser must be set up (leveled) perpendicularly in space, and secondly the optical axis of the emitted laser beam, the optical axis of the deflection means (particularly if the deflection means is a pentaprism, as is generally customary) and the mechanical rotation axis of the deflection means must be coaxial with respect to one another. By way of example, if the laser light source (usually a laser diode) is not positioned precisely and has a slant and/or an offset, then the optical axis of the laser beam is not coaxial with the optical axis and the mechanical rotation axis of the deflection means and an orientation error results. If the apparatus is not perpendicular, a leveling error results.
Rotation lasers known from the prior art are usually self-compensating rotation lasers, that is to say that they have means for initial, horizontal or vertical orientation of the laser beam and thus of the laser plane generated by the laser beam. For this purpose, a rotation laser can have an automatic leveling assembly, for example, that is to say that the apparatus upon start-up independently identifies its position relative to the horizontal or vertical plane and compensates for the ascertained deviation of the laser beam from the horizontal and/or vertical plane. The positional deviations of the apparatus can be detected by means of inclination sensors, for example, and the laser beam can then be oriented with the aid of motor-operated or hydraulic inclination compensators. In this case, the laser beam can be oriented for example by the adjustment of the inclination of the apparatus body, that is to say by a tilting mechanism situated in or on the exterior of the apparatus or on an apparatus mount, or by mechanical adjustment of optical components of the transmitting unit. What is disadvantageous is that the motors of the inclination compensators have a high energy consumption and a high inherent weight and, furthermore, require a relatively long time for the orientation of the laser beam. What is furthermore disadvantageous is that the self-leveling is typically possible only for positional deviations of up to approximately +/−5° from the horizontal and/or vertical plane.
The document U.S. Pat. No. 6,253,457 discloses a surveying apparatus, in particular a rotation laser, comprising an optical system comprising a plurality of lenses for correcting the exit angle of a laser beam, wherein the exit angle to be corrected is governed by an inclined position of the surveying apparatus in space. In this case, the exit angle can be corrected for example by the displacement of one or a plurality of lenses along the optical axis of the optical system or by a change in focus of a lens having a variable focus in the optical system. The lenses having a variable focus can be, inter alia, a liquid lens.
Besides the self-leveling of the rotation laser for compensating for positional deviations of the apparatus or, to put it another way, for compensating for angular deviations of the optical axis of the transmitting unit from the horizontal and/or vertical plane, it may additionally be necessary to compensate for further inaccuracies of the apparatus which can be caused, inter alia, by temperature influences or vibrations with respect to a misalignment of one or more components of the transmitting unit, e.g. of the laser light source and/or of one or more lenses of the optical system. In accordance with the prior art, such deviations can be compensated for e.g. by mechanical displacement of one or more lenses of the optical system, as described in U.S. Pat. No. 5,825,555, for example. What is disadvantageous, however, is that such a mechanical displacement of lenses is relatively slow and the weight of the rotation laser is relatively high by virtue of the requisite servomotors. Furthermore, the susceptibility to maintenance increases with the number of movable components in the rotation laser.